The United States Federal Communications Commission (FCC) is set to enact new regulations in 2005 to improve hearing aid compatibility (HAC) for hearing impaired users of mobile phones. As part of mobile phone HAC assessment, near field components of electro-magnetic fields are measured. The components are comprised of electric and magnetic fields.
FIG. 3 illustrates a typical electric field distribution for a flip-type mobile phone having a near field scan area as shown in FIG. 1 and a PCB outline as shown in FIG. 2. The dominant electric fields tend to occur at abrupt discontinuities of metallization such as at the edges of printed circuit boards (PCBs), shield cans, vibrators, and metallization patterns on the assembly. These discontinuities form concentrated electric currents on the metallic substrates that flow toward the edges of a substrate. When the current reaches an edge of a substrate, undesirable scattering of electro-magnetic fields occurs. The greater the magnitude of scattered fields, the more likely they are to interfere with hearing aid devices.
What is needed is a method, means, or apparatus for reducing the undesirable effects of electro-magnetic scattering at metallic discontinuities that exist within mobile phone designs.